1. Field of Invention
The present invention relates generally to the field of solid-state lasers and, more particularly, to geometries for diode-pumped solid-state lasers.
2. Discussion of Related Art
Solid-state lasers are limited in power scalability with good beam quality by thermo-optics effects. A geometry that exhibits relatively small thermo-optics effects is the grazing-incidence slab (also referred to as the grazing-incidence-disk). In these slabs, the optical gain is confined to a relatively thin region, typically less than about 2 millimeters (mm) thick. This thin region is referred to as the gain region. As shown in FIG. 1, a laser beam (optical signal) 102 is incident upon a thin region (gain region) 104 at a near-grazing incidence (a few degrees out of plane of the gain region 104), passes through the gain region, reflects at an optical surface 106 that bounds one side of the gain region, and then passes through the gain region again. The gain region 104 is pumped with diode radiation 108 directed at nominally normal incidence (i.e., at about 90 degrees or perpendicularly) to the plane of the gain region.
This implementation has relatively small thermal-optic effects because heat dissipated in the gain region 104 has only a short path to a heat sink (due to the thinness of the region), which limits the temperature rise. In FIG. 1, heat flow from the gain region 104 to the heat sink (not shown) is illustrated by arrows 110. In addition, since the whole optical signal (beam) 102 passes through the gain region 104, the thermal gradient is sampled equally by all parts of the optical signal, to the first order, thereby reducing thermo-optic effects. The dimension of the gain region 104 is controlled by either the optical absorption depth at the wavelength of the pump radiation 108 (pump wavelength) or the use of a gain element with a thin doped region. In either case, a high absorption coefficient at the pump wavelength is desired to maximize efficiency and allow the gain region 104 to be made as thin as possible.